The invention relates to an objective arrangement for an endoscope comprising a light exit that is angled in relation to a light entrance and comprising a deflection unit which guides an imaging beam path proceeding from the light entrance to the light exit. Here, the imaging beam path, in particular the marginal rays of the imaging beam path, defines a transmission region, a first reflection surface, and a second reflection surface within the deflection unit. If the imaging beam path is followed through the objective arrangement proceeding from the light entrance, said imaging beam path initially passes through the transmission region in order to be respectively reflected subsequently at the first reflection surface and, thereafter, at the second reflection surface. Consequently, the imaging beam path finally emerges at the light exit of the objective arrangement.
Such objective arrangements are known and used, for example, in endoscopes for imaging an object field which is angled in relation to a shaft axis of the endoscope such that the viewing direction on the object field extends at an angle of e.g. approximately 30° in relation to a longitudinal axis of the endoscope. Here, the endoscope can be embodied either as an endoscope, for example with a relay-lens system, eyepiece lens system or an attached optical fiber bundle, or else as a video endoscope with an integrated image sensor, the latter for example arranged at the distal end of the endoscope (a so-called “chip-in-tip endoscope”).
For the purposes of the beam deflection, the deflection unit in the objective arrangement in such endoscopes is typically embodied with two reflection planes, wherein the reflection planes may be arranged parallel to one another or in a manner extending in a convergent fashion and wherein reflection surfaces are embodied in the reflection planes.
Thus, known objective arrangements are often configured in such a way that the incident light initially passes through a first reflection plane in a transmission region in order subsequently to be reflected at a second reflection plane in a first reflection surface. Subsequently, the light that was reflected by the first reflection surface experiences a second reflection in a second reflection surface at a side of the first reflection plane that is facing away from the original direction of incidence of the light. Additionally, objective arrangements in which more than two reflections are used for the beam deflection are also known.
Until now, it has been conventional to embody the respective reflection surfaces on the reflection planes completely by reflective coatings in order to securely steer the light into a downstream image-side optical unit.